This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-160613, filed Jun. 8, 1999; and No. 2000-024199, filed Feb. 1, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to a catalyst for selective oxidation of carbon monoxide, a selective removing method of carbon monoxide, a hydrogen refining catalyst for selectively oxidizing CO and CH3OH of a gaseous mixture containing H2, CH3OH, CO and O2 and a hydrogen refining method for removing CO and CH3OH from a gaseous mixture containing H2, CH3OH and CO.
A polymer electrolyte fuel cell permits suppressing generation of a pollutant causing an air pollution, is high in its heat efficiency and, thus, is expected to be used widely as a low temperature operation type fuel cell in a motor car power source, a dispersed power source or the like. A platinum catalyst is used mainly in the electrode of the polymer electrolyte fuel cell. Since the platinum catalyst tends to be poisoned by carbon monoxide (CO), it is necessary remove CO from the fuel gas as much as possible. The fuel gas is manufactured by, for example, reforming the fuel such as methanol by means of steam reforming reaction or a partial oxidation reaction so as to produce a hydrogen gas. Then, CO formed as a by-product in the hydrogen manufacturing reaction is removed by a CO shift reaction of CO+H2O CO2+H2.
The removal of CO by the CO shift reaction is limited under the restriction in terms of the chemical equilibrium. For example, where a hydrogen gas is manufactured from methanol, followed by applying the CO shift reaction to the hydrogen-containing reaction mixture, the resultant gaseous composition contains about 40 to 60% of H2, about 10% of CO2, about 20% of H2O, and about 0.5% of CO. It should be noted that, in order to prevent the polymer electrolyte fuel cell from being poisoned by CO, it is necessary to lower the CO concentration to 100 ppm or lower. Such being the situation, it is necessary to take measures for further lowering the CO concentration in combination with the CO shift reaction.
As a measure for removing CO contained in the hydrogen-based raw material gas, studied is a method in which an oxidizing agent of O2 is added to the raw material gas and is brought into contact with the raw material gas so as to selectively oxidize CO contained in the raw material gas.
In the conventional catalyst, however, almost all the oxygen gas added to the raw material gas reacts with hydrogen, which is the main constituent of the raw material gas, so as to preferentially burn the hydrogen. As a result, CO is left unremoved from the raw material gas.
On the other hand, Japanese Patent Disclosure (Kokai) No. 6-296870 as claimed discloses a catalyst for cleaning the waste gas. It is taught that the catalyst consists of at least one metal selected from the platinum group elements, which is supported on a crystalline silicate having an X-ray diffraction pattern shown in Table A given in this prior art and represented in terms of the molar ratio of the oxide in a dehydrated state by a chemical formula (1xc2x10.8)R2O.[aM2O3.bMxe2x80x2O.cAl2O3].ySiO2, where R denotes an alkali metal ion and/or hydrogen ion, M denotes an ion of at least one element selected from the group consisting of VIII group elements, rare earth elements, Ti, V, Cr, Nb, Sb and Ga, Mxe2x80x2 denotes an ion of alkaline earth metals of Mg, Ca, Sr, Ba, 0 less than a, 0xe2x89xa6b less than 20, a+c=1, and 11 less than y less than 3000.
This prior art also teaches in columns [0008] to [0009] that the particular waste gas cleaning catalyst permits cleaning the waste gas containing NOx, CO and HC in accordance with reaction formulas (1) to (4) given below:
(1) C3H6+3/2O2xe2x86x923CH2O
(2) CH2O+O2xe2x86x92CO2+H2O
(3) CH2O+2NOxe2x86x92N2+CO2+H2O
(4) CO+1/2O2xe2x86x92CO2 
Reaction (1) given above represents activation of HC, reaction (2) represents combustion of HC, reaction (3) represents a denitrification, and reaction (4) represents combustion of CO.
An object of the present invention is to provide a catalyst for selectively oxidizing carbon monoxide, the catalyst being capable of selectively oxidizing CO contained in a gaseous mixture containing H2, CO and an oxidizing agent of O2.
Another object is to provide a selective carbon monoxide removing method that permits selectively removing CO from a gaseous mixture containing H2 and CO.
Another object is to provide a hydrogen refining catalyst capable of selectively oxidizing CO and CH3OH contained in a gaseous mixture containing H2, CO, CH3OH and an oxidizing agent of O2 with a high selective oxidizing capability.
Still another object is to provide a hydrogen refining method capable of selectively oxidizing and removing CO and CH3OH contained in a gaseous mixture containing H2, CO and CH3OH with a high removal rate.
According to a first aspect of the present invention, there is provided a selective carbon monoxide oxidizing catalyst capable of selectively oxidizing CO contained in a gaseous mixture containing H2, CO and an oxidizing agent of O2, comprising a carrier and an active metal consisting of at least one kind of metal selected from the group consisting of Pt, Pd, Ru, Rh and Ir and supported on the carrier, the carrier being a crystalline silicate having the highest to the fifth highest peaks in the powder X-ray diffraction using CuKxcex1 ray in the lattice spacing of 3.65xc2x10.1 xc3x85, 3.75xc2x10.1 xc3x85, 3.85xc2x10.1 xc3x85, 10.0xc2x10.3 xc3x85, and 11.2xc2x10.3 xc3x85, and having the composition represented by formula (1) under a dehydrated state:
(1xc2x10.8)R2O.[aM2O3.bNO.cAl2O3].ySiO2xe2x80x83xe2x80x83(1)
where R denotes at least one element selected from the group consisting of an alkali metal and H, M denotes at least one element selected from the group consisting of VIII group elements, rare earth elements, Ti, V, Cr, Nb, Sb and Ga, N denotes at least one element selected from the group consisting of Mg, Ca, Sr, and Ba, and the molar ratios a, b, c and y are: 0xe2x89xa6a, 0xe2x89xa6bxe2x89xa620, a+c=1, and 11xe2x89xa6yxe2x89xa63000.
According to a second aspect of the present invention, there is provided a selective removing method of carbon monoxide, comprising the step of bringing a gaseous mixture containing H2, CO and an oxidizing agent of O2 into contact with a selective oxidizing catalyst of carbon monoxide for selectively oxidizing and removing CO from the gaseous mixture, the selective oxidizing catalyst of carbon monoxide comprising a carrier and an active metal consisting of at least one kind of metal selected from the group consisting of Pt, Pd, Ru, Rh and Ir and supported on the carrier, the carrier being a crystalline silicate having the highest to the fifth highest peaks in the powder X-ray diffraction using CuKxcex1 ray in the lattice spacing of 3.65xc2x10.1 xc3x85, 3.75xc2x10.1 xc3x85, 3.85xc2x10.1 xc3x85, 10.0xc2x10.3 xc3x85, and 11.2xc2x10.3 xc3x85, and having the composition represented by formula (1) under a dehydrated state:
(1xc2x10.8)R2O.[aM2O3.bNO.cAl2O3].ySiO2xe2x80x83xe2x80x83(1)
where R denotes at least one element selected from the group consisting of an alkali metal and H, M denotes at least one element selected from the group consisting of VIII group elements, rare earth elements, Ti, V, Cr, Nb, Sb and Ga, N denotes at least one element selected from the group consisting of Mg, Ca, Sr, and Ba, and the molar ratios a, b, c and y are: 0xe2x89xa6a, 0xe2x89xa6bxe2x89xa620, a+c=1, and 11xe2x89xa6yxe2x89xa63000.
According to a third aspect of the present invention, there is provided a selective removing method of carbon monoxide, comprising the steps of:
preparing a reactor loaded with a catalyst bed housing a selective carbon monoxide oxidizing catalyst; and
passing a gaseous mixture containing H2, CO and an oxidizing agent of O2 through the reactor so as to selectively oxidize CO and, thus, remove CO from the gaseous mixture,
wherein:
the inlet temperature of the catalyst bed is set at 50 to 250xc2x0 C.; and
the selective carbon monoxide oxidizing catalyst comprises a carrier and an active metal consisting of at least one kind of metal selected from the group consisting of Pt, Pd, Ru, Rh and Ir and supported on the carrier, the carrier being a crystalline silicate having the highest to the fifth highest peaks in the powder x-ray diffraction using CuKxcex1 ray in the lattice spacing of 3.65xc2x10.1 xc3x85, 3.75xc2x10.1 xc3x85, 3.85xc2x10.1 xc3x85, 10.0xc2x10.3 xc3x85, and 11.2xc2x10.3 xc3x85, and having the composition represented by formula (1) under a dehydrated state:
(1xc2x10.8)R2O.[aM2O3.bNO.cAl2O3].ySiO2xe2x80x83xe2x80x83(1)
where R denotes at least one element selected from the group consisting of an alkali metal and H, M denotes at least one element selected from the group consisting of VIII group elements, rare earth elements, Ti, V, Cr, Nb, Sb and Ga, N denotes at least one element selected from the group consisting of Mg, Ca, Sr, and Ba, and the molar ratios a, b, c and y are: 0xe2x89xa6a, 0xe2x89xa6bxe2x89xa620, axc2x1c=1, and 11xe2x89xa6yxe2x89xa63000.
According to a fourth aspect of the present invention, there is provided a hydrogen refining catalyst for selectively oxidizing CO and CH3OH contained in a gaseous mixture containing H2, CO, CH3OH and an oxidizing agent of O2, the catalyst comprising a carrier and an active species supported on the carrier, the carrier being a crystalline silicate having the highest to the fifth highest peaks in the powder X-ray diffraction using CuKxcex1 ray in the lattice spacing of 3.65xc2x10.1 xc3x85, 3.75xc2x10.1 xc3x85, 3.85xc2x10.1 xc3x85, 10.0xc2x10.3 xc3x85, and 11.2xc2x10.3 xc3x85, and having the composition represented by formula (1) under a dehydrated state:
(1xc2x10.8)R2O.[aM2O3.bNO.cAl2O3].ySiO2xe2x80x83xe2x80x83(1)
where R denotes at least one element selected from the group consisting of an alkali metal and H, M denotes at least one element selected from the group consisting of VIII group elements, rare earth elements, Ti, V, Cr, Nb, Sb and Ga, N denotes at least one element selected from the group consisting of Mg, Ca, Sr, and Ba, and the molar ratios a, b, c and y are: 0xe2x89xa6a, 0xe2x89xa6bxe2x89xa620, axc2x1c=1, and 11xe2x89xa6yxe2x89xa63000.
According to a fifth aspect of the present invention, there is provided a hydrogen refining catalyst for selectively oxidizing CO and CH3OH contained in a gaseous mixture containing H2, CO, CH3OH and an oxidizing agent of O2, comprising a carrier consisting of a silicate and an active species consisting of Pd and supported on the carrier.
According to a sixth aspect of the present invention, there is provided a hydrogen refining method, comprising the step of bringing a gaseous mixture containing H2, CO, CH3OH and an oxidizing agent of O2 into contact with a hydrogen refining catalyst so as to selectively oxidize and remove CO and CH3OH from the gaseous mixture, the hydrogen refining catalyst comprising a carrier and an active species supported on the carrier, the carrier being a crystalline silicate having the highest to the fifth highest peaks in the powder X-ray diffraction using CuKxcex1 ray in the lattice spacing of 3.65xc2x10.1 xc3x85, 3.75xc2x10.1 xc3x85, 3.85xc2x10.1 xc3x85, 10.0xc2x10.3 xc3x85, and 11.2xc2x10.3 xc3x85, and having the composition represented by formula (1) under a dehydrated state:
(1xc2x10.8)R2O.[aM2O3.bNO.cAl2O3].ySiO2xe2x80x83xe2x80x83(1)
where R denotes at least one element selected from the group consisting of an alkali metal and H, M denotes at least one element selected from the group consisting of VIII group elements, rare earth elements, Ti, V, Cr, Nb, Sb and Ga, N denotes at least one element selected from the group consisting of Mg, Ca, Sr, and Ba, and the molar ratios a, b, c and y are: 0xe2x89xa6a, 0xe2x89xa6bxe2x89xa620, axc2x1c=1, and 11xe2x89xa6yxe2x89xa63000.
According to a seventh aspect of the present invention, there is provided a hydrogen refining method, comprising the steps of:
preparing a reactor loaded with a catalyst bed housing a hydrogen refining catalyst; and
passing a gaseous mixture containing H2, CO, CH3OH and an oxidizing agent of O2 through the reactor so as to selectively oxidize CO and CH3OH, thus, remove CO and CH3OH from the gaseous mixture,
wherein:
the inlet temperature of the catalyst bed is set at 50 to 250xc2x0 C.; and
the hydrogen refining catalyst comprises a carrier and an active species supported on the carrier, the carrier being a crystalline silicate having the highest to the fifth highest peaks in the powder X-ray diffraction using CuKxcex1 ray in the lattice spacing of 3.65xc2x10.1 xc3x85, 3.75xc2x10.1 xc3x85, 3.85xc2x10.1 xc3x85, 10.0xc2x10.3 xc3x85, and 11.2xc2x10.3 xc3x85, and having the composition represented by formula (1) under a dehydrated state:
(1xc2x10.8)R2O.[aM2O3.bNO.cAl2O3].ySiO2xe2x80x83xe2x80x83(1)
where R denotes at least one element selected from the group consisting of an alkali metal and H, M denotes at least one element selected from the group consisting of VIII group elements, rare earth elements, Ti, V, Cr, Nb, Sb and Ga, N denotes at least one element selected from the group consisting of Mg, Ca, Sr, and Ba, and the molar ratios a, b, c and y are: 0xe2x89xa6a, 0xe2x89xa6bxe2x89xa620, axc2x1c=1, and 11xe2x89xa6yxe2x89xa63000.
According to an eighth aspect of the present invention, there is provided a hydrogen refining method, comprising the step of bringing a gaseous mixture containing H2, CO, CH3OH and an oxidizing agent of O2 into contact with a hydrogen refining catalyst so as to selectively oxidize CO and CH3OH, thus, remove CO and CH3OH from the gaseous mixture,
wherein the hydrogen refining catalyst comprises a carrier consisting of a silicate and an active species consisting of Pd and supported on the carrier.
Further, according to a ninth aspect of the present invention, there is provided a hydrogen refining method, comprising the steps of:
preparing a reactor loaded with a catalyst bed housing a hydrogen refining catalyst; and
passing a gaseous mixture containing H2, CO, CH3OH and an oxidizing agent of O2 through the reactor so as to selectively oxidize CO and CH3OH, thus, remove CO and CH3OH from the gaseous mixture,
wherein
the inlet temperature of the catalyst bed is set at 50 to 250xc2x0 C.; and
the hydrogen refining catalyst comprises a carrier consisting of a silicate and an active species consisting of Pd and supported on the carrier.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.